This invention concerns a coiling machine for hot-rolled stock, such as strip or sheet, and the relative coiling method, as set forth in the respective main claims. The invention is applied in rolling lines for flat products to optimise, rationalise and accelerate the steps of forming the hot rolled coils performed downstream of the rolling train.
The invention is applied specifically with regard to the production of strip or sheet both with a thickness of between 0.5 and 5 mm, and also of more than 5 mm, with the temperature of the rolled stock at about 700÷800xc2x0 C. or more and with a production of around 20÷22 meters per second.
In the state of the art, there are a plurality of devices and apparatus to coil strip or sheet leaving the hot or cold rolling train, which perform their function more or less efficiently.
One type of coiling machine particularly used in the hot rolling of strip or sheet is the downcoiler, which includes at least two coiling mandrels arranged in sequence and below the plane on which the strip or sheet which has to be coiled passes.
This coiling system, although it is widely used, has problems both regarding the speed at which the coils are formed and also regarding the quality of the sheet obtained, especially in the case of products which are particularly thin.
In fact, in the case of thin strip or sheet, when the leading end is bent under the plane on which it is fed in order to be coiled onto the downcoiler, there may be problems caused in the quality of the product.
Moreover, coiling is not carried out in a repetitive manner since it is performed alternately on two downcoilers placed at different distances from the shears.
Another problem which is also linked to the thinness of the strip or sheet to be coiled is that the strip rubs against the runway which delivers it to the coiling machine, which can cause a deterioration in the surface quality of the strip or sheet.
Another problem is that with the systems known in the state of the art with a guide belt for initial winding, the winding speeds must necessarily remain low. A further problem is the lead-in of the strip during the initial winding step when thin strip is being produced.
A further disadvantage is the distance between the shears and downcoiler downstream due to the consequent dangers of blockages of the leading end of the rolled stock, and the problems of losing temperature due to radiance.
There is also the problem of the trailing end of the wound strip which knocks against the equipment during the braking step of the coil. It is also a problem to support the coiling mandrel as a cantilever.
A further problem is how to guide the strip without causing damage to the surface thereof.
The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art by providing a functional and extremely efficient solution both operationally and in terms of the quality of the product.
The invention is set forth and characterised in the main claims, while the dependent claims describe variants of the idea of the main embodiment.
The purpose of the invention is to provide a coiling machine for thin strip or sheet, and the coiling method which is achieved with the coiling machine, suitable to solve efficiently the above-mentioned shortcomings and in particular to guarantee efficiency, functionality and rationality to the coiling operations.
A further purpose is to obtain coiling conditions which will limit as much as possible any alterations to the characteristics of surface quality of the rolled stock to be coiled.
The coiling machine according to the invention is mounted at the outlet of a finishing train for strip or sheet of a thickness preferentially between 0.5 and 5 mm and travelling at a speed of around 20÷22 meters per second.
According to the invention, the coiling machine is located immediately downstream of a shears assembly which acts when the coiling of a coil is complete, and to prepare the leading end of the strip which will form the following coil.
The shears assembly, according to the invention, is arranged as near as possible to the coiling machine so as to reduce to a minimum the risks of blockages of the leading end of the strip.
According to a variant of the invention, the shears includes a positioning and holding frame which is associated with a movable capsule which carries the shearing blades and facilitates their replacement.
According to a variant, the capsule can be extracted/inserted axially to the axis of the blades.
According to a variant, the coiling machine comprises a retractable rollerway which intervenes when products of a greater thickness are to be worked; these cannot be coiled by the coiling machine according to the invention and are therefore translated downstream after the coiling machine has been excluded from the line or, in any case, has assumed a non-operative condition.
According to the invention, the coiling machine consists of a turntable assembly on which two coiling mandrels are mounted at a diametrically opposed position.
The turntable assembly may rotate to assume at least three positions, respectively a position of exclusion and two operating positions.
In the first position of exclusion, the two mandrels are both in a position of non-contact with the plane of feed of the rolled stock.
This position is assumed when rolled stock of great thickness is being produced, as the rollerway is placed in the operating position to deliver the rolled stock to conventional coiling machines, for example, downcoilers, or to cooling devices.
In the first operating position, a first mandrel is in a position where it substantially cooperates with the plane of feed of the rolled stock, and is waiting to receive the leading end of the rolled stock to be coiled, while a second mandrel is in a position which respectively may be to discharge the completed coil or end of coiling.
In this first operating position, the coiling of the strip is begun and carried out on the first mandrel, for a certain desired length.
In the second operating position, rotated substantially by 180xc2x0 with respect to the first operating position, the first mandrel moves to a position wherein coiling is completed, while the second mandrel is taken to a waiting position cooperating with the plane of feed of the rolled stock so as to form a second coil.
Therefore, the coiling method includes a repeated sequence of alternate coiling on one mandrel and the other, as the completed coil is discharged with means known to the state of the art from the mandrel before the same mandrel returns to the start-of-coiling position.
According to the invention, the coiling machine comprises, upstream of the turntable assembly and downstream of the shears, at least a movable guide blade arranged above the plane of feed of the rolled stock.
According to a variant, there are two movable guide blades, one below and one above the plane of feed of the rolled stock.
According to a variant, the upper movable guide blade is associated with a second movable guide blade, rotatable on the first and carrying at least a sliding roller in the free head.
The movable guide blades have an operating position wherein they support and guide the rolled stock cooperating with the plane of feed of the rolled stock and a position wherein they are substantially excluded from the plane of feed so as not to create interference.
The upper guide blade, moreover, includes a third position which it assumes during the cycle and in the transition phase between the two positions; in this position the upper guide blade grips the rolled stock as it is being coiled onto the mandrel located in its second position, and accompanies the rolled stock on its plane of feed so as to prepare it to be picked up by the other mandrel located in the first operating position.
According to the invention, the movable guide blades include slits on their surfaces which cooperate with the plane of feed of the rolled stock; the slits emit jets of air, liquid or a mixture thereof to support the rolled stock which is to be sent for coiling.
The pneumatic, hydraulic or mixed support prevents problems caused by friction on the surface of the rolled stock, which are considerable in the case of thin stock as in the invention and therefore it prevents a deterioration of the surface quality of the finished product.
Moreover, this support prevents the leading end of the rolled stock from overturning or bending, in the segment between the drawing assemblies and the mandrel, and thus prevents risks of blockages or impact with the equipment.
According to a variant, in cooperation with the jets of air there are driven rollers travelling at a speed greater than that of the strip and which have the effect of thrusting the strip itself, thus preventing blockages.
According to the invention, the mandrel located in the first operating position, wherein coiling is started and which cooperates with the plane of feed of the rolled stock, cooperates with an assembly of wrapper rollers mounted on articulated arms which come into outer contact with the rolled stock to be coiled, at several circumferential positions, thus facilitating and accelerating coiling.
According to a variant, the leading end of the strip as it arrives finds itself cooperating with at least two parallel and adjacent rollers which have the function of calendering the leading end of the strip.
The assembly of wrapper rollers is mounted on a trolley and can assume a non-operative position wherein the rollers open and do not come into contact with the rolled stock being coiled.
The non-operative position is assumed at least when the mandrel is passing from its first to its second operating position to complete coiling.
In its second operating position the mandrel cooperates with at least two movable assemblies from a working position to a non-working position.
To be more exact, according to the invention, there is at least an assembly to support the mandrel, which intervenes to support the shaft of the mandrel when the coil begins to have a considerable weight, and at least an assembly to support the coil equipped with rollers which are positioned from below into peripheral contact with the coil and facilitate coiling.
According to a variant, the assembly to support the mandrel operates according to the vectorial sum of the components of the weight and the drawing action.
According to a further variant, there are other movable assemblies equipped with rollers which, in the working position, come into contact with the coil to facilitate coiling and make it regular and uniform; they also prevent the trailing end of the strip, once the strip has been sheared and the coil is in the braking step, from knocking against the equipment and causing damage, and even from unwinding from the coil.
All these assemblies are movable, axially and/or rotationally, to move into a position of non-contact during the movements of the turntable assembly from its first to its second operating position and vice versa or in the position of exclusion.